Push-off attachment for lift trucks



5. w. SINCLAIR PUSH-OFF ATTACHMENT FOR LIFT TRUCKS May 11, 1965 3Sheets-Sheet 1 Filed Jan. 6, 1964 llllh.

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May 11, 1965 s. w. SINCLAIR 3,182,836

PUSH-OFF ATTACHMENT FOR LIFT TRUCKS Filed Jan. 6, 1964 3 Sheets-Sheet 2Jfuarf W. J//7/0// INVEN OR. m 41 W QM 52,11 AX/2%,???

May 11, 1965 S. W. SINCLAIR PUSH- OFF ATTACHMENT FOR LIFT TRUCKS 3Sheets-Sheet 3 Filed Jan. 6, 1964 ,URE 1,

United States Patent 3,182,836 PUSH-OFF ATTACENT FOR LIFT TRUCKS StuartW. Sinclair, Houston, Tex., assignor to Anderson,

The present invention relates to push-off attachments for lift trucks,and more specifically to a push-off attachment for use in removing aload from the tines of a fork lift truck, and improvements in theconstruction thereof.

In the past, push-off attachments have been either of the lazy tongsarrangement, a parallelogram arrangement orof the horizontal slidearrangement. Examples of these prior structures are found in the US.Patent Nos. 2,993,610; 2,619,241; 2,672,269; and 2,590,355. With thefirst two types, the sagging of the pusher plate, particularly when itis extended, has been somewhat of a problem. In the last type, the bulkand length of the device have presented maneuverability problems. It isan object of the present invention to overcome the foregoingdisadvantages of the prior art structures in a manner not previouslycontemplated.

Another object of the present invention is 'to provide 7 Yet anotherobject of the present invention is to provide a push-off attachmentwhichincludes pivoted yokes and pivoted equalizers set at 90from theyokes, so as to prevent sagging of the pusher plate when fully extended,and at the same time allows the attachment to be folded into a verysmall unit when thepusher plate is retracted.

A still further object of the present invention is to provide a push-offattachment which includes hydraulic motor means for actuation thereof,whichtmotor means may be placed in such a position that it does notsubstantially increase the overall width of the attachment when thepusher plate is fully retracted. A particular advantage of thisarrangement is that it allows the pusher plate to be shiftedhorizontally by means of other typical lift truck attachments, thusincreasing the overall versatility of the unit. e

A. further object of the present invention is to provide extends andretracts the pusher plate in exact proportion to the volume of fluid inthe motor, so that movement of the pusher plate is uniform.

Other further objects, features and advantages will be apparent from thefollowing description of presently preferred embodiments of theinvention, given for the purpose of disclosure, taken in conjunctionwith the accompanying drawings, where like character referencesdesignate like parts throughout the several views and where: V V

FIGURE 1 is aside View of a lift truck which includes the presentinvention thereon in the act of discharging aloadfrom the fork tines, V

FIGURE 2 is an enlarged partial side view, partially in section,showingiindetail the attachment of FIG- FIGURE 3 is a top view,partially in section, of the attachment of FIGURE 2, V

FIGURE 4 is a front view, partially in section, of the :attachment ofFIGURE 2, Q

a a push-off attachment wherein the hydraulic motor means 3,182,33Fatentecl May 11, 196

FIGURE 5 is a side view, similar to FIGURE 2, of modification of thepresent attachment, and

FIGURE 6 is a side view showing the attachment FIGURE 5 when retracted.

The invention generally comprises a frame, a pair hinged or pivotedyokes, a pair of hinged or pivote equalizers set at from the yokes, andmeans for e: tending and retracting a pusher plate relative to the framiReferring now to the drawings, and particularly 1 FIGURE 1, thereference numeral 19 generally refer to a conventional fork lift truckwhich includes a ma; 12 to which are attached vertically movable forktines 1 by means of the bracket 16. In such trucks 10, mear 18 areconventionally provided for raising and lowerin the tines 14. Attachedalso to the bracket 16 is the pusl off attachment 20 of the presentinvention, which will t described in greater detail hereinafter.Generally, hov ever, the push-off attachment 20 includes the vertic:pusher plate 22 which may be horizontally traversed rel; tive to themast 12, so that a load 24 carried on the tint 14 may be pushed off orpulled on the tines by the li: truck 10. Although not shown, the pusherplate 22 ma have various pallet grippers mounted thereon to expan theuse of the lift truck 10, in a manner similar to'thos illustrated in thepatents previously mentioned. As suc pallet grippers form no part of thepresent invention, the are not illustrated.

Referring now to FIGURE 2, the push-off attachmei 26 will be explainedin greater detail; Attached to tl bracket 16, in any suitable mannersuch as by welding, 21 frame 26. Pivotably attached to the frame 26 is are; yoke 28, and pivotably attached to the rear yoke 28 is tt front yoke30. In turn, the front yoke 39 is pivotably at tached to the pusherplate 22. The pivotable attachmen in each instance are all parallel,here shown as horizonta and include the hinges 32, 34 and 36respectively.

With reference now to FIGURES 3 and 4, it will t noted that both therear and frontyokes 28 and 30 get erally resemble large letter Cs whichare joined back 1 back by means of a group of three hinges 34, while tlextended ends of the yoke are joined respectively to tl: frame 26 andplate 22 by a pair of hinges 32 and 36. A though three pairs of hinges34 are shown, this is a me] matter of convenience and a greater orsmaller numb: may be utilized. It is to be particularly noted that t!hinges 32 are parallel to the hinges 34 and that the hingi 34 areparallel to the hinges 36, consequently the plate 2 will be parallel tothe frame 26 at all times.

Referring again to FIGURE 2, pivotably attached 1 the frame 26 is a rearequalizer 38, and pivotably attache and are here shown as the verticalhinges 42, 44 and 4 respectively.

As can be seen by comparing FIGURES 2, 3, and the hinges 42, 44, and '46are all parallel, consequentl the pusher plate '22 is prevented fromdropping or sa, ging with reference to the frame 26. Furthermore, sinrthe equalizers 38 and 40 are ,mounted at right angles '1 the yokes 23and 3%, it is apparent ,th atzthe hinges 32 at 42 define a plane whichis parallel "to the plane define by the hinges 36 and 46. A furtherplane is defined t the h inges 34 and 44, which is likewise parallel totl previously mentioned planes. Consequently, the push plate 22 is heldvertically and parallel to the mast 1 no matter what its extension fromthe frame 26.

Because the front and rear yokes 28 and are t shaped, it is possible forthe pusher plate 22 to be grea ly retracted and for the foldedequalizers 38 and at to 2 within the open ends of the yokes so that theentire a tachment 22 forms a very-compact unit. Thus, as sec in FIGURE3, the length of either equalizer 38 or 4 ess than the distance betweenthe ends of either yoke or 30. With reference again to FIGURE 2, thereference nural 48 generally refers to the means for traversing oracting and extending the pusher plate'22, and is here wn as a hydraulicmotor. The hydraulic motor genlly consists of a cylinder 50 having apiston 52 slidy mounted therein. The cylinder 50 is attached to the ryoke 28 by means of a bracket 54 and pivotable con- :tion 56 on theplate 70. The piston 52 is attached the front yoke 30 by the connectingrod 58 and pivote connection 60 on the lug 72. Fluid pressure supmeans62 and 64 are connected to the cylinder 50 that hydraulic fluid mayenter therethrough to recipate the piston 52 within the cylinder 50. Ascan be n in FIGURE 3, a pair of identical means 48 are proed, althoughit would be well within the skill in the to delete or add additionalunits. the pusher plate 22 generally comprises a flat plate ose outeredges 66 are turned back, thereby forming generally rectangular pan.When the pusher plate 22 fully retracted, the rolled back edges 66 coverthe opting mechanism as an additional safety advantage. th referenceparticularly to FIGURE 4, it will be noted vt there are several cut outs68 in the front of the plate in order that the hinges 34 and 36 mayextend thereough. In this manner, when the plate 22 is fully rected, theover-all width of attachment 249 is reduced. With reference again toFIGURE 2, the double-headed ow immediately above the plate 22 shows thedirecnal movement of the plate relative to the frame 26. ren fullyretracted, the plate 22 is shown in dotted lines 22'. In a similarmanner, the double-headed arrow we the means 48 shows the relativemovement of the ans when retracting and extending the pusher plate 22. eretracted position of the means 48 is shown in dotted as as 48'. [t isto be noted that the particular disposition of the ans 48 is such thatsimilar triangles are produced. at is to say, that the triangle formedwith its apex as hinge 34 and its two legs terminating at the hinges and36 is similar to the triangle with its apex 34 and two legs terminatingat the pivotable connections 56 i 60. Consequently, the reaction of themeans 48 on smaller similar triangle produces a linearproportionmovement in the yokes 28 and 30, and therefore the sher plate20. In this manner, advantageously, the esent invention provides apush-off attachment wherein movement of the pusher plate 20 is directlypropornal to the volume of fluid introduced into the cylinder sothat'the operator need not make adjustments to in-tain a uniformtraverse speed. [n use, the fork lift truck 10 is maneuvered until the'k tines 14 may be inserted beneath the load 24. ereupon, the pusherplate 22 may be retracted against mast 12 by inducing hydraulic fluidthrough the fluid :ssure means 64 to activate the piston 52, which inturn tws the connecting rod 58 into the cylinder 50, thus iwing thepivotable connections 56 and 60 together. is in turn draws the hinge 36towards the hinge 32, :reby retracting the pusher plate 22 against theframe to the position shown as '22 in FIGURE 2. At this re, orsimultaneously with the previously described tion, the truck maybe movedforward so that the tines under the load 24 thereby allowing the truck16 to lift load and maneuver it to any desired position. To remove theload 24 from the tines 14, fluid i in ced through the fluid pressuremeans 62, thereby pushthe piston 52 and the connecting rod 58 so thatthe 'otable connections 56 land 60 are moved apart. This turn causes thehinge 36 to move away from the hinge thereby extending the pusher plate22. Atv the same is, the combination of the yokes 28 and 30 and theualizers 33 and t prevent the pusher plate 22 from sagging and maintainit in a position which is .at all times parallel to the frame es.

With reference now to FIGURES 5 and 6, a modification of the deviceshown in FIGURE 2 is illustrated, wherein the majority of the variouselements are substantially identical to those previously described, andhence have been given identical numbers. In this modification, it willbe noted that the means 48 is aligned substantially vertically insteadof horizontally as in FIG- UR-E 2. The particularly advantageous resultobtained thereby is seen in FIGURE 6, wherein it will be noted that themeans 48 remains substantially vertical and does not extend any greatdistance behind the frame 26 as does the comparable means 48' in FIGURE2.

It should be further noted when comparing FIGURES 5 and 2 that thecylinder 5t? is attached to the front yoke 36 and connecting rod 58 isconnected to the rear yoke 28 in FIGURE 5, while the parts are reversedin FIGURE 2. In any event, it is to be noted that the same similartriangles as shown in FIGURE 2 exist in FIGURE 5 such that the triangleformed by the hinges 74, '76, and 34 is similar to the triangle formedby the hinges 32, 36, and 34. Consequently, the same linear motionproduced by the device of FIGURE 2 is produced by the device of FIG- URE5. Said another way, the similar triangles of FIG- URE 5 have merelybeen rotated, but still remain similar and in addition to providing thesame function as before, advantageously allow the cylinder 50 to bemounted more compactly.

As before, the means 458 for traversing or retracting and extending thepusher plate 22 is here shown as a hydraulic motor. The hydraulic motorgenerally consists of a cylinder 54} having a piston 52 slidably mountedtherein. The cylinder 50 is attached to the rear yoke 28 by means of abracket '78'and pivotal connections 76 on the lug 86 which forms a partof the yoke 30. The piston 52 is attached to the rear yoke 28 by theconnecting rod 58 and pivotal connection 74 on the plate 82 which formsa part of the rear yoke 28. Fluid pressure supply means 34 and 86 areconnected to the cylinder 50 so that bydraulic fluid may entertherethrough to reciprocate the piston 52 within the cylinder 50. Justas was shown in FIGURE 3, a pair of identical means 48 may be provided,although it would be well within the skill in the art to delete or addadditional units.

Upon the introduction of hydraulic fluid to the cylinder 50, themovement of the hinge 34' and the pusher plate 22 respectively are shownrelative to the frame 26 by the double-headed arrows above these items.Thus, upon the introduction of hydraulic fluid through the supply means84, the piston 52 is activated and the pivotal connection 74 is pushedfurther from the pivotal connection 76, thus resulting in traversing thepusher plate 22 by extending it from the frame 26 by means of thereaction on the rear and front yokes 28 and 3%. To retract the pusherplate 22, hydraulic fluid is introduced through the supply means 86,thus pushing the piston 52 within the cylinder 50 and drawing thepivotal connections 74 and 76 together, which in turn react upon therear and front yokes 28 and 30. The position of this modification whenfully retracted is shown in FIGURE 6. The use of the traversing of thepusher plate 22 of the modification shown in FIGURES 5 and 6 isidentical to that described hereinabove with reference to FIGURES 1-4.

Thus, advantageously, the present invention has provided :a push-offattachment which is quite rigid, even when fully extended, and whichfolds into a small unit adjacentto the lift truck body when retracted,as well as providing the other advantages previously mentioned.

The present invention, therefore, is well adapted to carry out theobjects and attain the ends and advantages mentioned as well as othersinherent therein. While presently preferred embodiments of the inventionhave been given forrthe purpose of disclosure, numerous changes in thedetails of construction, and the combination, shape,

size, arrangement of parts and uses may be resorted to without departingfrom the spirit and scope of the invention as hereinafter claimed.

.What is claimed is:

1. The combination with a fork lift truck having a vertically movablebracket of apush-ofi attachment including:

a vertical frame attached to the bracket, a first C-shaped yoke, asecond C-sh'aped yoke, the yokes pivotally connected back to back, avertical pusher plate, the ends of the first yoke horizontally pivotallyconnected to the frame, the ends of the second yoke horizontallypivotally connected to the pusher plate, a first equalizer, a secondequalizer, the equalizers pivotally joined, the first equalizervertically pivotally connected to the frame, the second equalizervertically pivotally connected to the pusher plate, a hydraulic motorincluding a cylinder and a piston, the cylinder pivotally connected toone of the yokes,

. each yoke.

3. The invention of claim 1 wherein the cylinder i mounted substantiallyhorizontally.

4. The invention of claim 1 wherein the cylinder i mounted substantiallyvertically.

References Cited by the Examiner UNITED STATES PATENTS 2,787,393 4/57Horton 2l45l 2,975,923 3/61 Ulinski 2l4-514 I FOREIGN PATENTS 122,0752/59 U.S.S.R.

HUGG O. SCHULZ, Primary Examiner.

GERALD M. FORLENZA, Examiner.

1. THE COMBINATION WITH A FORK LIFT TRUCK HAVING A VERTICALLY MOVABLEBRACKET OF A PUSH-OFF ATTACHMENT INCLUDING: A VERTICAL FRAME ATTACHED TOTHE BRACKET, A FIRST C-SHAPED YOKE, A SECONS C-SHAPED YOKE, THE YOKESPIVOTALLY CONNECTED BACK TO BACK, A VERTICAL PUSHER PLATE, THE ENDS OFTHE FIRST YOKE HORIZONTALLY PIVOTALLY CONNECTED TO THE FRAME, THE ENDSOF THE SECOND YOKE HORIZONTALLY PIVOTALLY CONNECTED TO THE PUSHER PLATE,A FIRST EQUALIZER, A SECOND EQUALIZER, THE EQUALIZERS PIVOTALLY JOINED,